Free tool · No signup
Thumbnail A/B Preview
Put two thumbnail versions next to each other at every size viewers actually see, and pick the stronger one before you publish.
- 100% free
- No signup
- Runs in your browser
Step by step
How to use the Thumbnail A/B Preview
Step 01
Upload version A and version B (both stay in your browser).
Step 02
Compare them at feed, search and sidebar sizes.
Step 03
Pick the one that survives the squint test at the smallest size.
Understand your results
What the results mean
Thumbnails compete at small sizes — in the suggested sidebar a thumbnail is barely wider than your thumb. Comparing two versions side by side at each real size exposes which one loses its message when shrunk.
This is a visual comparison, not a live test: it tells you which version reads better, not which gets more clicks. For statistical testing on a published video, use YouTube Studio's built-in "Test & compare", which rotates up to three thumbnails on your real audience.
FAQ
Frequently asked questions
How do I A/B test YouTube thumbnails?
For live statistical testing, use YouTube Studio's own 'Test & compare' feature. Use this preview before publishing, to eliminate the weaker design early.
What should I compare between versions?
Readability of any text at sidebar size, emotional clarity of faces, contrast against YouTube's white and dark backgrounds, and whether each version makes you curious without the title.
Why does small-size comparison matter most?
A large share of impressions happen at small sizes (sidebar, mobile). A thumbnail that only works large is optimized for the wrong screen.
Do you store my images?
No. Both images stay in your browser; nothing is uploaded.
Is this tool free?
Yes — free, client-side, no account.
Last updated November 4, 2026 · Reviewed by the channelpeeker team · How we calculate
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